1. Field of the Invention
The invention relates to an electric bulb for an illuminated sign and, in particular, to a height adjustable bulb for an illuminated sign.
2. Description of Related Art
Generally, an identification lamp or illuminated sign comprises a bulb and a flat lantern case or housing for accommodating the bulb to show noticeable identifications created by opening(s) in panels of the housing with emitting and shadowing patterns at both sides.
The lamp or bulb known today is conventionally an incandescent bulb. With such a point-source bulb, the light from ID lamp is not homogeneous, and a troublesome beam spot is observable. Furthermore, the bulb suffers from high power consumption and short life.
A solution for these problems has been disclosed in China Patent No. 97204601.1, titled xe2x80x9cElectric Bulb for Identification Lampxe2x80x9d, filed on Jan. 2, 1997 by the applicant and authorized by Chinese Patent Office on Jul. 30, 1998. In such solution, however, the novel bulbs include light emitting diodes (LEDs). Such bulbs must be made in different sizes to substitute for different sizes of incandescent bulbs, since the height of each novel bulb is fixed. Thus, The lamp bulb described in China Patent No. 97204601.1 lacks in the ability of being interchangeable, and there is a need for a better solution.
Therefore, The primary object of the invention is to provide a body height adjustable bulb for an illuminated sign emitting homogeneous light with low power consumption and long life-time.
Another object of the invention is to provide an illuminated sign comprising such an electric bulb.
To attain these objects, a body height adjustable lamp bulb according to the invention is comprised of a bulb body, a bulb head, a connector, a plurality of light emitting diodes (LEDs) positioned around the periphery of the bulb body, and a power supply unit for the LEDs.
The lamp bulb further comprises a height adjusting unit inserted into an open end of the bulb body having proper friction between them such that the height of the bulb body can be adjusted by a force directed against the friction, the connector is fixed on the bulb head at one end, and the another end connects to a joint end of the height adjusting unit such that the bulb body can be rotated by a proper torque.
The components of the power supply unit are set within the bulb body or the height adjustable unit.
With the configuration described above, in a body height adjustable ID lamp bulb according to the invention, the well-distributed light can be obtained by rotation of the bulb and thus changing the direction of emitted light, and the height of bulb body can be adjusted by the movement of the body height adjusting unit to substitute for incandescent bulbs of different sizes. In addition to these advantages, the power consumption is lower, and the life expectancy is longer. The adjustable features are not only useful for the lamp bulb but also applicable to any lamps requiring adjustment of light emitting direction.